As for the defects specific to the man, the author mentions them in his statement:
“If a woman finds her husband to be emasculated”—that is, his penis has been severed. He did not say, “If his emasculation is established,” because emasculation can be known from her side. Thus, if she says that her husband is emasculated, this is a defect, since it defeats the purpose [of marriage]. Among women’s greatest purposes are bearing children, enjoyment, and pleasure through intercourse, whereas his penis has been severed.
His statement, “or he has only what is insufficient for intercourse, she may annul the marriage,” means that only a small part of his penis remains, with which he is unable to have intercourse. Its presence is therefore like its absence.
His words indicate that if enough remains for intercourse to be possible, it is not a defect, even though full sexual enjoyment is lost. Thus, if, for example, only the extent of the glans or something similar remains—something with which intercourse is possible, but sexual enjoyment cannot be attained—it is not a defect.
His statement, “If his impotence is established by his admission”: impotence is derived from ʿinān (a rein used to lead a she-camel), and it means being restrained from intercourse. The suitability of this derivation is clear: just as a bridle restrains a camel, impotence restrains a person from intercourse—meaning that he is unable to have intercourse with his wife. This may arise later in life, or it may be natural; and, according to the sounder view, it may also arise later in life. Thus, his impotence is established by his admission, such as when he acknowledges it before the judge.
His words, “by his admission,” indicate that it is not established merely by the woman’s claim unless she produces evidence. If she says, “He is impotent,” her statement is not accepted without evidence, due to the Prophet’s saying: “The burden of proof is upon the claimant.” (1)